In terms of visual aspects and artistic direction, Diablo 4 returns to the more grounded gothic theme of Diablo 1 and 2. The game also improves upon these foundations with respect to how equipment looks, towns and terrain contain richer details and the general atmosphere of the game is more immersive compared to its predecessors. Combat animations for melee, spells etc. are more fluid and natural which lends to a smoother experience.
In terms of game mechanics, however, Diablo 4 lacks sufficient depth as an ARPG. It does not excel in any key area such as itemization, character builds, mob diversity and bosses. All of these issues culminate in a shallow end game for the more dedicated players where the sense of progression is lost in the simplicity of the game design.
Itemization is lackluster. There exists only a handful of uniques. The majority do not provide any interesting mechanics, abilities or stats that would define or at least significantly change the way a particular build or skill operates for a class. Normal (white) and magic (blue) items are made almost immediately useless as there does not exist any mechanic that would allow these item groups to be used as bases for crafting. There exists no set items, class-locked items, runewords (or similar system for socketed items) that could provide further character customization. Item bases also have no meaningful differences (e.g. a plate helm and a cap have the same defence values if they are the same item level). No stat requirements apply either to equip these items meaning that you do not have to consider for example your strength or dexterity values when making item choices.
The lack of character customization is further amplified by a lack of stat depth. By ‘stat depth’ I mean that desirable stats are homogenized across all classes (e.g. all classes need vulnerability). The pool of stats is also too streamlined. There exists, for example, no magic find, block rate, accuracy rate, faster hit recovery, faster hit rate, life leech %, prevent monster heal etc. CC reduction is compiled into a single stat (Control Impaired Duration Reduction) instead of being divided into different categories such as Cannot Be Frozen or Reduced Poison Length. The simplicity causes a negative feedback loop on itemization and character builds.
A positive aspect is that Diablo 4 tries to introduce mechanics that allows the player to use several abilities during combat instead of repeatedly spamming one or two abilities (e.g. D2 blizzard sorc or Zealadin etc.). Unfortunately, the simplicity of the skill tree in combination with a paragon board that appears to be a much more streamlined version of Path of Exile:s skill tree simply doesn’t lend enough complexity that would allow for a higher level of character customization.
Mob diversity is too constrained. You will, for example, see the same red ghosts in many areas with no distinctive features from one another. The lack of distinctiveness is amplified by the game’s level scaling. The scaling causes the player to experience a homogenized world. There is no clear separation between different areas with key mobs at certain power levels that you can associate those areas with.
In summary, Diablo 4 does not really stand out and for players that are looking for a more ‘crunchy’ ARPG without necessarily emulating Path of Exile are left feeling bored after the novelty wears off post-campaign.